Cameron has been going to extreme lengths to convince voters the Tories care about the environment - at the weekend he was ostentatiously strolling around in shoes made from recycled car seats and firemen's trousers. But Redwood, who got his nickname over his resemblance to Star Trek alien Mr Spock, has blown his boss's efforts out of the water with his online diary claims.

He rubbished the idea that pollution was causing global warming, calling it a "swindle". And he added: "Things are not entirely as the consensus supposes."

He also mocked concerns over gasguzzling cars by saying: "Visits to Mars by space probes detect global warming there - but have not yet discovered the 4x4s causing it." Environment Minister Ian Pearson said the comments were insulting to millions worldwide already feeling the devastating effects of climate change.

Mr Pearson added: "His statements are an affront to the millions at risk of flooding in Bangladesh, severe famine in Africa and drought in China and India."

Last night Redwood tried to defend his remarks. He said: "If you read my blog in full you will see that what I was saying is we should get on with managing the consequences of global warming."

Redwood has a nasty habit of putting his foot in it. His most famous gaffe came in 1995 when as Welsh Secretary he tried to sing the principality's national anthem - and was filmed mouthing words he did not know.

Last year he revealed Tory plans to privatise the road network. In 2004 he bizarrely accused the government of murdering fish.

Paul Charles from Virgin Atlantic said: "Taxing passengers has failed as a means of reducing the growth in emissions. Taxing passengers more would damage the UK economy as it would make airlines less competitive and shift jobs to other countries."

Budget airline Flybe said the proposals were "bad for the economy and an attempt to turn the clock back to a time when air travel was the preserve of the rich."

Meanwhile, shadow home secretary David Davis yesterday said race-row Tory Patrick Mercer should "eventually" get his job back. Ex-colonel Mercer was sacked as Tory security spokesman by Cameron last week for suggesting he had known many "idle and useless" ethnic minority soldiers. Mr Davis said: "He has paid the price."

Chancellor Gordon Brown will today call on the UN to make the fight against global warming a top priority.

Mr Brown will also say Mr Cameron would be unable to lead a green campaign because the Tories have no credibility within the EU.